Method of manufacturing electrical cable, and resulting product, with reduced required installation pulling force

ABSTRACT

Disclosed are cable types, including a type THHN cable, the cable types having a reduced surface coefficient of friction, and the method of manufacture thereof, in which the central conductor core and insulating layer are surrounded by a material containing nylon or thermosetting resin. A silicone based pulling lubricant for said cable, or alternatively, erucamide or stearyl erucamide for small cable gauge wire, is incorporated, by alternate methods, with the resin material from which the outer sheath is extruded, and is effective to reduce the required pulling force between the formed cable and a conduit during installation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/015,688, filed Jun. 22, 2018, which is a continuation of U.S.application Ser. No. 15/590,881, filed May 9, 2017, which is acontinuation of U.S. application Ser. No. 14/858,872, filed Sep. 18,2015, which is a continuation of U.S. application Ser. No. 14/144,150,filed Dec. 30, 2013, now issued as U.S. Pat. No. 9,142,336 on Sep. 22,2015, which is a continuation of U.S. application Ser. No. 13/774,677,filed Feb. 22, 2013, now U.S. Pat. No. 8,616,918, issued Dec. 31, 2013,which is a continuation of U.S. application Ser. No. 13/274,052, filedOct. 14, 2011, now U.S. Pat. No. 8,382,518, issued Feb. 26, 2013, whichis a continuation of U.S. application Ser. No. 12/787,877, filed May 26,2010, now U.S. Pat. No. 8,043,119, issued Oct. 25, 2011, which is acontinuation of U.S. application Ser. No. 11/675,441, filed Feb. 15,2007, now U.S. Pat. No. 7,749,024, issued Jul. 6, 2010, which is acontinuation-in-part of U.S. application Ser. No. 11/120,487, filed May3, 2005, now abandoned, which is a continuation-in-part of U.S.application Ser. No. 10/952,294, filed Sep. 28, 2004, now U.S. Pat. No.7,411,129, issued Aug. 12, 2008. Each patent and patent applicationidentified above is incorporated here by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to electrical cables, more particularly toTHEN electrical cables, and even more particularly to methods forreducing the surface coefficient of friction and required installationpulling force thereof, as well as preferred pulling lubricantcompositions for effecting such reductions.

BACKGROUND OF THE INVENTION

Electrical cables include a conductor core and typically include anouter jacket or sheath. The term “sheath,” as used herein and throughoutthe specification and claims, is defined to mean the outermostprotective jacket or covering surrounding a conductor core, whether of asingle type material or multiple layers of the same or differentmaterial. The conductor core may typically be, for example, a singlemetal wire, multiple small wires twisted together to make a “stranded”cable, or multiple insulated wires or other type electrical conductorsacting together to serve a particular function (e.g., three-phaseconnection). The sheath may comprise one or more layers of polymeric orother material to provide physical, mechanical, electrical insulatingand/or chemical protection for the underlying cable components. For thepurpose of type THHN cable of the present invention, the exteriorportion of the sheath is of nylon. Specifically, type THHN cablecomprises a conductor core of a single solid or stranded conductor,surrounded by a layer of polyvinyl chloride (PVC) electrical insulation,covered by an outer layer of nylon.

Installation of electrical cable often requires that it be pulledthrough tight spaces or small openings in, and in engagement with,narrow conduits, raceways, cabletrays, or passageways in rafters orjoists. This becomes problematic since the exterior surface of the cablesheath normally has a high coefficient of friction, therefore requiringa large pulling force. Moreover, installation parameters include maximumallowable cable pulling tension and/or sidewall pressure limits.Exceeding these limits can result in degradation of the cable, physicaldamage and inferior installation.

To overcome this problem, the general industry practice has been to coatthe exterior surface of the cable sheath with a pulling lubricant at thejob site in order to reduce the coefficient of friction between thissurface and the conduit walls or like surfaces, typically usingvaselines or lubricants produced specifically, and well known in theindustry for such purpose, such as Yellow 77® (hereinafter, “Y 77”). Theterm “pulling lubricant,” as used herein and throughout thespecification and claims, is defined to mean lubricating material whichsufficiently reduces the coefficient of friction of the exterior surfaceof the sheath of the cable to facilitate the pulling of the cable.

The aforementioned industry practice of applying a pulling lubricantlike Y 77 to the finished cable at the job site poses problems,principally due to the additional time, expense and manpower required tolubricate the finished cable surface at the job site as well as to cleanup after the lubricating process is completed. Alternative solutionshave been tried but are generally unsuccessful, including the extrusionof a lubricant layer over the extruded polymeric sheath during themanufacturing of the cable, or the application of granules of materialto the still-hot sheath during the extrusion process, which granules aredesigned to become detached when the cable is pulled through the duct.However, these solutions not only require major alterations of themanufacturing line, but result in a loss in manufacturing time,increased economic costs, and undesirable fluctuations in thegeometrical dimensions of the cable sheaths.

It is also important to an understanding of the present invention toknow the difference between what are referred to as “pulling lubricants”and what are “processing lubricants.” A pulling lubricant is a lubricantthat appears at the outside surface of the sheath of the cable and iseffective to lower the surface coefficient of friction such as to reducethe force necessary to pull the cable along or through building surfacesor enclosures. A processing lubricant is lubricating material that isused to facilitate the cable manufacturing process, such as the flow ofpolymer chains during any polymer compounding as well as during theextrusion processes while the polymer is in its molten or melt phase.Cable manufacturers have long used processing lubricants, such asstearic acid or ethylene bis-stearamide wax, as a minor component of thepolymeric compound from which the cable sheath is formed. Because aprocessing lubricant is normally not effective except when the polymeris in this melt phase, the effect of a processing lubricant isessentially non-existent in the final hardened polymer sheath of thecable. Even where there may be an excessive amount of the processinglubricant, a separate pulling lubricant would still be required tosufficiently reduce the cable sheaths' exterior surface coefficient offriction in order to minimize the pulling force necessary to install thecable.

Accordingly, there has been a long-felt need for an effective method ofproviding a pulling lubricant at the exterior surface of the finishedcable, and particularly the finished THEN cable, which is effective toreduce the cable surface coefficient of friction and minimize therequired installation pulling force, without incurring the inconvenienceand time-consuming operation and expense associated with the applicationof the pulling lubricant at the installation site, nor significantlyincreasing the complexity and cost of the manufacturing process, norundesirably altering the geometrical characteristics of the cablesheaths.

SUMMARY OF THE INVENTION

The process of the present invention accomplishes these objectives forTHHN cable by a cable manufacturing process in which a particularpulling lubricant, of optimum weight percentage or quantity, isintroduced into the manufacturing process at a particular stage ofmanufacture, which results in the pulling lubricant being present in theouter sheath, so that it is available to reduce the coefficient offriction of the exterior sheath surface when the cable is to beinstalled. Depending upon the material of the sheath and the type oflubricant, this may be as a consequence of the migration, or delayedmigration or “blooming,” of the pulling lubricant to the sheath surface;or alternatively, due to the permeation of the pulling lubricantthroughout the sheath. Under these circumstances, the pulling lubricantis effective to lower the surface coefficient of friction below that ofthe inherent coefficient of friction of the material from which theouter layer of the THHN sheath is formed, thereby reducing the requiredinstallation pulling force.

In accordance with the process of the invention, and as described belowin greater detail, the pulling lubricant is selectively chosen toprovide the optimum results with respect to the particular nylon sheathmaterial, and may alternately be introduced into the THHN cablemanufacturing process at various stages, ranging from the initialcompounding of the lubricant with the polymeric nylon material to formlubricated pellets from which the sheath is to be formed, to mixing thelubricant with the nylon sheath material before introduction of themixture into the extrusion process, to its introduction into the sheathextrusion process while the nylon sheath forming material is in itsmolten state.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other details and aspects of the invention, as well as theadvantages thereof, will be more readily understood and appreciated bythose skilled in the art from the following detailed description, takenin conjunction with the accompanying drawings, in which:

FIG. 1 is a diagrammatic representation of typical equipment used in themanufacture of cable in accordance with the present invention, whenmixing the lubricant with the nylon material prior to extrusion;

FIG. 2 is a graphical representation of test data comparing the effectof different pulling lubricants in small size THEN cable in which theouter sheath material is nylon;

FIG. 3 is a graphical representation of test data comparing both theeffects of different pulling lubricants and different percentages ofpulling lubricant in large size THHN cable in which the outer sheathmaterial is nylon;

FIGS. 4 and 5 are representations of test devices which may be used tocreate the aforementioned test data;

FIG. 6 is a section view of a THEN cable produced in accordance with theprocess of the present invention;

FIG. 7 is a diagram illustrating a first type of joist-pull testapparatus used to characterize the present invention; and

FIG. 8 is a diagram illustrating a modified type of joist-pull testapparatus used to characterize the present invention.

DESCRIPTION

Referring initially to FIG. 1, there is depicted typical equipment 11for manufacturing electrical cable 12 in accordance with one process ofthe present invention. The outer sheath of the cable is of an extrudedpolymer material, specifically nylon. The equipment 11 may include areel 13 which supplies conductor wire 14 to an extruding head 15. Inflow communication with the extrusion head is a tank 16 of the nylonpellets 17. A tank 18 with the desired pulling lubricant 19 is adaptedto be in flow communication with the tank 16 by way of conduit 22, thusenabling the mixing of the pulling lubricant with the nylon pellets 17,the mixture thereafter introduced into the extruder. Alternatively, thetank may be adapted to be in fluid communication with the extruder orextrusion head 15, by way of conduit 23, downstream from the point ofentry of the nylon material, thus allowing the pulling lubricant to mixwith the nylon material while in its molten state in the extruder orextruder head. A cooling box 20 for cooling the extruded product isprovided, and a reel 21 is positioned for taking up the resulting cableassembly 12. When the final cable construction is such that there aremultiple layers of sheath material, the pulling lubricant shoulddesirably be incorporated into the outermost layer.

As is therefore evident, the pulling lubricant can be mixed with thematerial from which the outer sheath is to be extruded prior toextrusion or, alternatively, introduced into the extruding head forsubsequent mixing with the molten extrusion material as the sheath isbeing formed. As a further alternative, the pulling lubricant can beinitially compounded with the polymeric material of the pelletsthemselves in a process upstream of that depicted in FIG. 1, therebyforming lubricated polymeric pellets, thus eliminating the need for tank18 and conduits 22 and 23.

Polymeric materials that can be used for an insulating layer or outersheath of different type of cable include polyethylene, polypropylene,polyvinylchloride, organic polymeric thermosetting and thermoplasticresins and elastomers, polyolefins, copolymers, vinyls, olefin-vinylcopolymers, polyamides, acrylics, polyesters, fluorocarbons, and thelike. As previously described, for the THEN cable of the presentinvention, the conductor core of a single solid or stranded conductor issurrounded by an insulating layer of PVC covered by an outer sheath of apolyamide (e.g., nylon).

In accordance with the testing subsequently described, it has beendetermined that, for THHN cable, silicone oil is the preferred pullinglubricant. For small gauge THEN wire, erucamide is an alternativepreferred pulling lubricant, to be incorporated in the nylon sheath.

The efficacy of these pulling lubricants for the nylon sheath, andspecifically an optimum range for the quantity of such lubricants, inaccordance with the invention, has been proven by the use of varioustests. Prior to discussing the results of such tests, these test methodsand their equipment are described as follows:

Testing Methods

Coefficient of Friction Test

Referring now to FIG. 4, diagrammatically illustrated is the apparatusfor a coefficient of friction test. The coefficient of friction testapparatus was developed to give a consistent way to determine the inputvalues necessary to use the industry-standard program published byPolyWater Corporation to calculate a real-world coefficient of frictionfor a given cable being pulled in conduit. Given the inputs for theconduit setup, the back tension on the wire, and the pulling tension onthe pulling rope, this program back-calculated a coefficient of frictionfor the cable by subtracting the back tension from the pulling tensionand attributing the remaining tension on the rope to frictional forcesbetween the cable and the conduit.

The overall setup used a pulling rope threaded through ˜40′ of PVCconduit (appropriately sized for the cable being pulled) with two 90°bends. Three 100′ pieces of THHN cable were cut and laid out parallel toone another in line with the first straight section of conduit, and therope connected to them using industry-standard practice. The other endof the THHN cable was attached to a metal cable which was wrapped arounda cylinder with an air brake to allow the application of constant backtension on the setup.

The metal cable was threaded through a load cell so that it could bemonitored in real-time, and continuously logged. The pulling rope wassimilarly threaded through a load cell and constantly monitored andlogged. Values for both back tension and pulling tension were logged forthe time it took to pull cable through the conduit run. These valueswere then averaged and used in the PolyWater program to calculatecoefficient of friction.

Specific Type THHN Tests

Initial tests of small gauge Type THHN wire were performed using thesmall-scale tension tester shown in FIG. 5. In this test, multipleindividual American Wire Gauge (AWG) size 12 THHN wires were provided onthe payoff and attached to a metal pulling tape that was threadedthrough an arrangement of ½″ conduit that included about 50 feet ofstraight conduit and four 90° bends. A pulling rope was attached to theother end of the pulling tape and a tugger was used to pull the cablearrangement through the conduit. The rope was threaded through a pulleyarrangement that used a load cell to monitor rope tension while the wirewas pulled through the conduit. This tension was continuously logged andaveraged to give an average pulling force for the pull. This forcecorrelated directly to the coefficient of friction for the cable.

Using the data obtained from the small scale pull test of FIG. 5, FIG. 2illustrates a comparison of the different required pulling forces for asmall gauge cable consisting of multiple (AWG) size 12 THEN conductors.The test subjects had 0.25-0.85% of two different potential pullinglubricants, erucamide and stearyl erucamide, mixed into the outer nylonsheath. Results of the test are shown in FIG. 2 and compared to theresults for the standard THHN product without any pulling lubricant andwith the externally applied industry-standard Y77. This test shows thaterucamide is one preferred lubricant for small gauge THEN cable, in anoptimum percentage of approximately 0.85%, by weight.

Next, large gauge Type THEN cable was tested. Using the coefficient offriction test of FIG. 4, FIG. 3 illustrates the different values ofsurface coefficient of friction of the exterior surface of the sheath,for cables consisting of three individual large gauge AWG 4/0 THHNconductors, for varying percentages of the pulling lubricant, siliconeoil, of varying molecular weights. The two lubricants compared in FIG. 3are a high-molecular weight silicone oil (HMW Si) and a lower molecularweight silicone oil (LMW Si). Comparison results are shown for this sameTHHN cable arrangement lubricated with industry-standard Y77, as well aswith respect to three other trial pulling lubricants, fluorinated oil,molydisulfide, and stearyl erucamide. The results in FIG. 3 illustratethat, while other pulling lubricants can reduce the coefficient offriction of the exterior surface of the cable, the preferred pullinglubricant for THHN cable, and particularly large gauge THHN cable, is ahigh molecular weight silicone oil added at a level of approximately 9%,by weight, or higher.

In accordance with an advantage of the present invention, the pullinglubricant that is incorporated in the sheath is present at the outersurface of the sheath when the cable engages, or in response to thecable's engagement with, the duct or other structure through which thecable is to be pulled. For the THHN cable of the present invention,where the outer sheath is of nylon and the preferred pulling lubricantis high molecular weight silicone oil, this silicon-based lubricantpermeates the entire nylon sheath portion and is, in effect,continuously squeezed to the sheath surface in what is referred to asthe “sponge effect,” when the cable is pulled through the duct.

Compounding with Pulling Lubricant

As previously described, the pulling lubricant may be incorporated intothe extruded sheath (or the outer layer of the cable sheath if thesheath is of multiple layers) by initially compounding the lubricantwith the (outer) sheath material to be extruded. To prepare thelubricated blend of the present invention, the resin and additionalcomponents, including the pulling lubricant, are fed into any one of anumber of commonly used compounding machines, such as a twin-screwcompounding extruder, Buss kneader, Banbury mixer, two-roll mill, orother heated shear-type mixer. The melted, homogeneous blend is thenextruded into strands or cut into strips that may be subsequentlychopped into easily handled pellets. The so-prepared lubricated pelletsare then fed into the extruder for forming the outer sheath.

THHN Cable

THHN and THWN-2 are types of insulated electrical conductors that covera broad range of wire sizes and applications. THHN or THWN-2 conductorsare typically 600 volt copper conductors with a sheath comprising anouter layer of nylon surrounding a layer of thermoplastic insulation andare heat, moisture, oil, and gasoline resistant. THEN cable is primarilyused in conduit and cable trays for services, feeders, and branchcircuits in commercial or industrial applications as specified in theNational Electrical Code and is suitable for use in dry locations attemperatures not to exceed 90° C. Type THWN-2 cable is suitable for usein wet or dry locations at temperatures not to exceed 90° C. or not toexceed 75° C. when exposed to oil or coolant. Type THHN or THWN-2conductors are usually annealed (soft) copper, insulated with a tough,heat and moisture resistant polyvinylchloride (PVC), over which apolyamide layer, specifically nylon, is applied. Many cables, includingthose addressed by the present invention, can be “multi-rated,”simultaneously qualifying for rating as THHN or THWN-2.

Referring now to FIG. 6, there is illustrated a THHN cable 24constructed in accordance with the process of the invention. The cableis characterized by a sheath comprising an extruded layer 25 of PVCinsulation material and an overlying extruded thin layer 26 of nylon,the sheath surrounding a central electric conductor 27 which is usually,though not exclusively, of copper. The only limitation on the type ofpulling lubricant to be incorporated into the extruded outer nylonsheath is that it be sufficiently compatible with nylon to beco-processed with it, and particularly when compounded with nylon, thatit be robust enough to withstand the high processing temperature fornylon, which is typically about 500° F. However, it has been found thatfor THHN cable, this lubricant is preferably a high molecular weight,high viscosity silicone fluid; for small gauge THHN wire, as analternative, erucamide or stearyl erucamide.

Two industry-standard processes can be used to produce this product, theso called co-extrusion method and the tandem extrusion method. In bothprocesses, the conductor, either solid or stranded, is first introducedinto the extrusion head where the heated, melted PVC insulation compoundis introduced and applied to the circumference of the conductor. In theco-extrusion process, the melted nylon compound is introduced into thesame extrusion head and applied together with the PVC to the conductor,in a two-layer orientation. In the tandem process the PVC-coatedconductor leaves the first extrusion head and is introduced into asecond, separate extrusion head where the melted nylon is applied to thesurface. In both cases, the final product is then introduced into acooling water bath and ultimately the cooled product is wound ontoreels. In either case, the nylon material is preferably initiallycompounded with the pulling lubricant to provide the so-lubricatedextrusion pellets.

As shown in FIG. 2, small gauge THHN cable prepared, as described, withnylon as the outer layer of the sheath, and containing 0.25%, 0.50% and0.85%, by weight, of stearyl erucamide, had an average pulling force of18.1 lbs, 16 lbs and 18.5 lbs, respectively. Even better, small gaugeTHHN cable containing 0.25%, 0.50% and 0.85%, by weight, of erucamidehad an average pulling force of 13.2 lbs, 10.3 lbs and 9.6 lbs,respectively. Comparably, the pulling force for a THHN cable with nopulling lubricant was measured at 38.5 lbs, and THHN cable with only Y77 applied to the exterior surface was measured at 15.3 lbs. FIG. 3, onthe other hand, illustrates the results when silicone oil is used inTHHN cable, compared to other potential lubricants, illustratingsilicone oil as a much preferred pulling lubricant for this type cable.

To understand the effects of the jacket lubricant system on the ease ofpull, variations of the UL (Underwriters Laboratories, Inc.) joist pulltest were utilized.

The joist pull test outlined in UL719 Section 23 establishes theintegrity of the outer PVC jacket of Type NM-B constructions whensubjected to pulling through angled holes drilled through wood blocks.

The first variation of the test apparatus (see FIG. 7) consists of anarrangement of 2″×4″ wood blocks having holes drilled at 15° drilledthrough the broad face. Four of these blocks are then secured into aframe so that the centerlines of the holes are offset 10″ to createtension in the specimen through the blocks. A coil of NM-B is placedinto a cold-box and is conditioned at −20° C. for 24 hours. A section ofthe cable is fed through corresponding holes in the blocks where the endprotruding out of the last block is pulled through at 45° to thehorizontal. The cable is then cut off and two other specimens are pulledthrough from the coil in the cold-box. Specimens that do not exhibittorn or broken jackets and maintain conductor spacing as set forth inthe Standard are said to comply.

Pulling wire through the wood blocks provides a more direct correlationof the amount of force required to pull NM-B in during installation.Because of this relationship, the joist-pull test is initially the basisfor which ease of pulling is measured, but a test for quantifying this“ease” into quantifiable data had to be established.

Accordingly, and as shown in FIG. 8, a variable-speed device wasintroduced to pull the cable specimen through the blocks. Anelectro-mechanical scale was installed between the specimen and thepulling device to provide a readout of the amount of force in thespecimen. To create back tension a mass of known weight (5-lbs) was tiedto the end of the specimen.

Data recorded proved that NM-B constructions having surface lubricatesreduced pulling forces.

A 12-V constant speed winch having a steel cable and turning sheave wasemployed; the turning sheave maintains a 45 degree pulling angle andprovides a half-speed to slow the rate of the pulling so that more datapoints could be obtained. Holes were drilled in rafters wherebyspecimens could be pulled by the winch.

It was found using this method that lubricated specimens yieldedapproximately a 50% reduction in pulling force when compared tostandard, non-lubricated NM-B specimens. The results are shown in Tables1 and 2 wherein the data was recorded at five second intervals.

TABLE 1 Specimen Description Test Pt. Manufacturer ManufacturerManufacturer Manufacturer Manufacturer Manufacturer Control ControlPresent Descr. A1 A2 A3 B1 B2 B3 1 2 Invention 1^(st) Point 26.8 48.337.8 37.4 16.5 41.9 24 2^(nd) Point 34.6 51.1 35.2 38.1 41.6 42 20.53^(rd) Point 33.7 46.8 32 33 40.2 38.7 20 4^(th) Point 38.6 49.8 34.734.6 41.3 29.5 17.4 5^(th) Point 33.1 44.8 34.2 32.5 41.3 34.3 20.26^(th) Point 28.6 44.7 32.2 33.2 42.5 35.9 15.8 7^(th) Point 5.5 51 32.233.9 41.1 37 17.2 8^(th) Point 26.8 49.2 33.9 33 40.9 38.4 17.3 9^(th)Point 21.9 52.5 32.6 30.6 42.7 37.3 21.9 Average 30.51 48.69 33.87 34.0341.45 37.22 19.37 AAA- Denotes OutliersTest in Table 1 performed at a constant speed with winch using ½ speedpulleyTest in Table 2 performed on cable with 5# weight suspended at buildingentryStd. Prod.

Average Present Invention 37.6289 19.37

TABLE 2 Specimen Description Test Pt. Manufacturer A Manufacturer BControl 1 Control 2 Control 3 Invention A Invention B Descr. 14-2 14-214-2/12-2 14-2/12-2 14-2/12-2 14-2/12-2 14-2/12-2 1^(st) Point 34 32.650 47.5 40.2 21.5 12.3 2^(nd) Point 35 35.7 50.6 38.3 37.5 22.9 12.83^(rd) Point 35.5 31.2 46.7 43.2 27.5 29 12.1 4^(th) Point 37.7 35 44.546 36.8 22.4 14.9 5^(th) Point 40.5 30.6 46.2 39.5 36 23.3 11.9 6^(th)Point 32.9 28.8 40.9 35.7 41.2 21.1 12.5 7^(th) Point 44.2 32.4 52.837.5 37 21.6 11.7 8^(th) Point 43 32.4 40.7 27.7 31.7 22.5 11.7 9^(th)Point 43.4 30.5 40 31.1 19.2 11 10^(th) Point 40 11.6 Average 38.6232.13 45.82 38.50 35.99 22.61 12.25 14-2/12-2 14-2/12-2 14-2/12-2Control Avg. Invention A Invention B 40.103241 22.61 12.25

Although the aforementioned description references specific embodimentsand processing techniques of the invention, it is to be understood thatthese are only illustrative. For example, although the description hasbeen with respect to electrical cable, it is also applicable to othertypes of non-electrical cable such as, for example, fiber optic cable.Additional modifications may be made to the described embodiments andtechniques without departing from the spirit and the scope of theinvention as defined solely by the appended claims.

That which is claimed: 1) A thermoplastic high heat-resistantnylon-coated (THEM) electrical cable having reduced installation pullingforce through a polyvinyl chloride (PVC) conduit setup, the THENelectrical cable comprising: at least one conductor capable of carryingan electrical current through the THEN electrical cable, wherein theconductor is formed at least in part from copper; and, a sheath forprotecting the conductor, wherein the sheath comprises: an insulatinglayer surrounding the conductor and providing electrical insulation tothe conductor, wherein the insulating layer is formed at least in partfrom extruded polyvinyl chloride (PVC); and, an outer layer surroundingthe insulating layer, wherein the outer layer further comprises; anextruded nylon component; a pulling lubricant incorporated in theextruded nylon component that aids in reducing the installation pullingforce as the THEN electrical cable is pulled through a PVC conduitsetup; and wherein, the pulling lubricant is silicone based; and thepulling lubricant is present in at least a portion of the outer layer;and further wherein, the outer layer is both resistant to heat,moisture, oil and gasoline, and provides the THEN electrical cable withthe physical characteristic of having an average coefficient of frictionagainst an interior surface of a PVC conduit setup of less than about0.25. 2) The thermoplastic high heat-resistant nylon-coated (THEN)electrical cable of claim 1, wherein the silicone based pullinglubricant comprises a high molecular weight silicone based pullinglubricant. 3) The thermoplastic high heat-resistant nylon-coated (THEN)electrical cable of claim 1, wherein the THHN electrical cable has thephysical characteristic of having an average coefficient of frictionagainst an interior surface of a PVC conduit setup of less than about0.2. 4) The thermoplastic high heat-resistant nylon-coated (THEN)electrical cable of claim 1, wherein the THHN electrical cable has thephysical characteristic of having an average coefficient of frictionagainst an interior surface of a PVC conduit setup of between about0.125 and about 0.2. 5) The thermoplastic high heat-resistantnylon-coated (THEN) electrical cable of claim 1, wherein the THHNelectrical cable has the physical characteristic of having an averagecoefficient of friction against an interior surface of a PVC conduitsetup of less than about 0.15 6) The thermoplastic high heat-resistantnylon-coated (THEN) electrical cable of claim 1, wherein the pullinglubricant comprises a low molecular weight silicone based pullinglubricant. 7) The thermoplastic high heat-resistant nylon-coated (THEN)electrical cable of claim 1, wherein the at least one conductorcomprises a plurality of grouped conductors. 8) The thermoplastic highheat-resistant nylon-coated (THEN) electrical cable of claim 1, whereinthe at least one conductor is a large gauge conductor. 9) Thethermoplastic high heat-resistant nylon-coated (THEN) electrical cableof claim 8, wherein the at least one conductor comprises an AWG 4/0conductor. 10) The thermoplastic high heat-resistant nylon-coated (THEN)electrical cable of claim 1, wherein the THHN electrical cable has around profile. 11) The thermoplastic high heat-resistant nylon-coated(THEN) electrical cable of claim 1, wherein the THHN electrical cable israted for use in dry locations at temperatures not to exceed 90° C. 12)The thermoplastic high heat-resistant nylon-coated (THEN) electricalcable of claim 1, wherein the THHN electrical cable is rated to carrycurrent at voltages not to exceed 600 Volts. 13) The thermoplastic highheat-resistant nylon-coated (THEN) electrical cable of claim 1, whereinthe PVC conduit setup includes at least two 90° bends. 14) Thethermoplastic high heat-resistant nylon-coated (THEN) electrical cableof claim 13, wherein the PVC conduit setup includes a first straightsection of conduit connected to a first one of the 90° bends, a secondstraight section of conduit connected between the first one of the 90°bends and a second one of the 90° bends, and a third straight section ofconduit connected to the second one of the 90° bends. 15) Thethermoplastic high heat-resistant nylon-coated (THEN) electrical cableof claim 14, wherein the first straight section of the conduit is about30′ long, the second straight section of the conduit is about 5′ long,and the third straight section of the conduit is about 10′ long. 16) Athermoplastic high heat-resistant nylon-coated (THHN) electrical cablehaving reduced installation pulling force through a polyvinyl chloride(PVC) conduit setup, the THEN electrical cable comprising: at least oneconductor capable of carrying an electrical current through the THHNelectrical cable, wherein the conductor is formed at least in part fromat least one metal; and, a sheath for protecting the conductor, whereinthe sheath comprises: an insulating layer surrounding the conductor andproviding electrical insulation to the conductor, wherein the insulatinglayer is formed at least in part from extruded polyvinyl chloride (PVC);and, an outer layer surrounding the insulating layer, wherein the outerlayer further comprises; an extruded nylon component; a pullinglubricant that aids in reducing the installation pulling force as theTHEN electrical cable is pulled through a PVC conduit setup; andwherein, the pulling lubricant is present in at least a portion of theouter layer; and wherein, the pulling lubricant is permeable through thenylon component after the nylon component has been extruded and can besqueezed therefrom when the THHN electrical cable is pulled through aPVC conduit; and further wherein, the outer layer is both resistant toheat, moisture, oil and gasoline, and provides the THEN electrical cablewith the physical characteristic of having an average coefficient offriction against an interior surface of a PVC conduit setup of less thanabout 0.25. 17) The thermoplastic high heat-resistant nylon-coated(THEN) electrical cable of claim 16, wherein the PVC conduit setupincludes at least two 90° bends. 18) The thermoplastic highheat-resistant nylon-coated (THEN) electrical cable of claim 17, whereinthe PVC conduit setup includes a first straight section of conduitconnected to a first one of the 90° bends, a second straight section ofconduit connected between the first one of the 90° bends and a secondone of the 90° bends, and a third straight section of conduit connectedto the second one of the 90° bends. 19) The thermoplastic highheat-resistant nylon-coated (THEN) electrical cable of claim 18, whereinthe first straight section of the conduit is about 30′ long, the secondstraight section of the conduit is about 5′ long, and the third straightsection of the conduit is about 10′ long.